1. Field of the Invention
The present invention relates to a transaction handling system for handling transactions by transmitting and receiving data by means of a central unit, terminal control equipment and terminal devices through communication lines or signal lines or by wireless communication.
2. Description of the Prior Art
In a prior art automatic cash dispenser (CD) of a banking system, in order to check to see if a user who wants to effect a transaction by use of the CD is a valid user, a magnetic card having a secret code specified by a customer or an account number is issued to the customer when he or she registers a new account. Then, when the customer tries to effect a transaction by use of the CD, the customer inserts the magnetic card into the CD and keys in the secret code to the CD, and the entry of transaction data is permitted only if the keyed-in secret code and the secret code recorded on the magnetic card are the same, thereby to identify that the user of the CD is a valid user who knows the secret code recorded on the magnetic card. Many other unauthorized use prevention systems for checking the validity of the user of the machine by using a secret code have been used.
In the prior art unauthorized use prevention system of the type commonly used, a check is made to see if an operator who wants to effect a transaction by use of a stationary machine such as a CD is a valid operator who knows a predetermined key word to prevent an unauthorized transaction.
In recent years, a portable terminal device which is carried by a bank solicitor to a customer site and is connected to a central unit from the customer site through a telephone line to transmit data to permit a transaction has been put into practice. It may be possible that such a device can be stolen and an unauthorized transaction carried out by the use of a stolen device, or an unauthorized transaction may be carried out by a device not permitted for use in a particular system. For example, a portable terminal device owned by a bank B may be connected to a central unit of a bank A which is designed to effect a transaction by connecting to only the portable terminal devices owned by the bank A, or a microcomputer expert may build a device having the same performance as the portable terminal device owned by the bank A and connect it to the central unit of the bank A to effect an unauthorized transaction Consequently, unauthorized use prevention for a system which uses a portable terminal device connected to the central unit through a public communication line to effect a transaction cannot be attained by merely checking the validity of the operator who operates the machine by the secret code like the unauthorized use prevention system for the CD.